1. Field of the Invention
The invention relates to an electric oil pump system.
2. Description of Related Art
There has been proposed an electric oil pump system that is a combination of an oil pump that circulates fluid (oil) and an electric motor that drives the oil pump. The electric motor includes a rotor that rotates and a stator that is fixedly arranged radially outward of the outer peripheral face of the rotor. The rotor is formed by arranging a plurality of permanent magnets on the outer peripheral face of a rotary drive shaft along its circumferential direction. The rotary drive shaft is a rotary shaft that is shared by the electric motor and the oil pump. In addition, there has been proposed an electric oil pump system in which a stator of an electric motor is fixed by screwing bolts passed through a housing of an oil pump, to a motor housing (refer to, for example, Japanese Patent Application Publication No. 2005-98268). Further, the stator of the electric motor is integrated, through resin molding, with insulators on which coils are wound.
However, if the oil pump and the electric motor are fastened to each other via a resin mold portion with bolts, the resin mold portion of the stator is brought into contact with a metal face of the housing of the oil pump. This contact portion may be creep-deformed due to age deterioration. Thus, for example, warpage of the stator and loosening of bolts may occur. As a result, a rotary shaft of the electric motor may cause rotation fluctuation. Further, there may be caused contact noise between internal teeth and external teeth in a rotor portion of the oil pump, operating noise of the electric oil pump system due to pulsation of pump discharge pressure, and reduction in pump output (pressure, flow rate).